| Abstract
| - Even though the formidably laborious and time-consuming nature of oligosaccharide analysis limits certain attempts to analyze the glycosylation profile, the significantelucidation of carbohydrate modifications is largely dependent on it. Aiming to substantially improve the samplepreparation procedure, a novel protocol allowing glycan-specific detection in the presence of other species, suchas tryptic peptides, on MALDI-TOF was proposed andthen evaluated. The new protocol is based on the conceptthat the desorption/ionization efficiency of glycans couldbe selectively and substantially enhanced while drasticallysuppressing the other ion species upon glycan-selectivederivatization. A series of known and novel labelingreagents, all of which carry hydrazide functionality to allowglycan-specific derivatization, were prepared and evaluated in terms of their abilities to enhance the detectionsensitivity of glycans, suppress ions of other contaminants(e.g., peptides), and detect acidic oligosaccharides. Several novel reagents that possess hydrophobic residue(s)together with quaternary ammonium/pyridinium or guanidino functionalities significantly enhanced the detectionsensitivity of oligosaccharides. When enzymatically deglycosylated tryptic ovalbumin digest was directly derivatized by these reagents and subjected to MALDI-TOFanalysis without any prior purification, we observed thata single type of analyte ion (labeled glycan) could suppressa large majority of peptide ions while allowing a low-femtomole level detection of oligosaccharides. The efficacyof this approach was further evaluated using several othermodel glycoproteins, including α1-acid glycoprotein thatcontains a variety of sialylated oligosaccharides.
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